Short Answers to Hard Questions About Antibiotic Resistance

The idea of people dying from infections that were once easily cured may seem outlandish. But it is happening already — taking about 23,000 lives in the United States a year — and experts warn that things will get worse because bacteria are becoming resistant to antibiotics faster than we can make new drugs to fight back.

We have ourselves to blame, for overusing the drugs in people and squandering them on livestock. Now, a dangerous form of drug resistance has reached the United States, leaving us just one step away from infections that are completely untreatable.

What is antibiotic resistance?

It used to be that infectious diseases were the biggest killers of Americans — illnesses like tuberculosis and pneumonia. The invention of antibiotics, which were developed for medical use in the 1940s, changed all that. But they became overused, and the bugs they were invented to fight started to develop ways of resisting them. For some years now, infectious disease doctors have been warning that unless we rein in use of antibiotics in both people and livestock, there will come a day when they will be powerless against the most ferocious bugs, turning the clock back to the early years of the 20th century.

What is CRE?

CRE, which stands for carbapenem-resistant Enterobacteriaceae, is the most fearsome family of germs because it is resistant even to last-resort antibiotics.

The only drug that reliably treats CRE is colistin, an old and inexpensive drug that came on the market more than 50 years ago. This week researchers reported that they had discovered a gene in a bacteria that makes bugs resistant to colistin. It was found in a strain of E. coli in the urine of a patient in Pennsylvania. The patient was successfully treated, but if that gene makes its way into a strain of CRE, the bug would be unstoppable.

“We depend on colistin for the worst of the worst,” said Dr. James Johnson, a professor of medicine and an infectious disease expert at the University of Minnesota. “If it is knocked out, in most cases we really have nothing.”

Should I be scared?

Not yet. The discovery does not mean that an otherwise healthy person with a urinary tract infection is in danger of dying from it. (The Pennsylvania woman eventually recovered because her infection was treatable with antibiotics.) But the gene is mobile and can be picked up by other bugs — in sewer systems, in animal feed lots, in people’s guts or urinary tracts. That can make more bugs more resistant. The biggest worry is that a strain of CRE will pick up the gene. That could be devastating for anyone who is suffering from a CRE infection. “That is the combination we are all afraid of,” said Dr. Lance Price, a researcher at George Washington University.

For now, CRE is rare. The CRE germs cause about 600 deaths a year, usually strike people receiving medical care in hospitals or nursing homes, including patients on breathing machines or dependent on catheters. Healthy people are rarely affected.

How has antibiotic resistance changed medicine?

Dr. Johnson from Minnesota says the spread of resistant bugs means doctors are having to blast patients’ infections with increasingly stronger antibiotics. That has led to more patients coming in with infections caused by the C. difficile, a gut germ that flourishes when the patient has taken a lot of antibiotics. (The germ was estimated to cause almost half a million infections in the United States in 2011, and 29,000 people died within 30 days of the initial diagnosis.) Doctors now frequently send patients home with setups for intravenous antibiotics because pills no longer do the trick. Sometimes the specter of resistant infections can delay or cancel surgeries.

Why aren’t there more new antibiotics?

Most drug companies are not eager to make them. Compared with other drugs, antibiotics are not big moneymakers, and some manufacturers have gotten out of the business. Most people take antibiotics just once in a while, for a short time — unlike drugs for blood pressure, high cholesterol or diabetes, which most patients will take every day for the rest of their lives. When a new antibiotic comes out, doctors may hesitate to prescribe it, wanting to keep it in reserve for tough infections that older drugs cannot cure. Once the drug gets more widespread use, germs may become resistant to it, and doctors will quit prescribing it. So an antibiotic that required lots of time and money to develop may have a short life on the market. Infectious disease experts are working with Congress and the Food and Drug Administration to try to find ways to create financial incentives for drug companies to invest in making new antibiotics.

Is there anything I can do to protect myself?

A few simple steps can help reduce your risk of picking up a dangerous bug, says Dr. Brad Spellberg, chief medical officer for Los Angeles County+USC Medical Center. Wash your hands frequently. If you get sick, try not to use antibiotics. “What you should be doing is saying to the doctor, ‘Do I really need these antibiotics?’ ” he said.

Since hospitals are incubators of dangerous germs, if you end up in one, try to get out as fast as you possibly can. As for whether to avoid meat raised with antibiotics, Dr. Spelling says there is some evidence that such meat is more likely to have resistant germs, but those are avoidable with proper cooking.

Is there any real harm in taking an antibiotic for a cold?

There are several risks. An important one is based on the fact that healthy people normally carry billions of bacteria in their noses, throats, skin, genitals and gut. Antibiotics change the balance of those microbes, killing off susceptible ones and allowing drug-resistant ones to flourish. Even after a person finishes a course of antibiotics, the excess of drug-resistant bacteria can persist for months. If those drug-resistant bacteria find their way into the urinary tract — and normal gut bacteria are a common source of urinary infections — they can cause a drug-resistant infection that may be difficult to treat. In addition, people constantly pass bacteria — including drug-resistant ones — to their close contacts, so they may put others at risk.

Why are antibiotics given to livestock?

The vast majority of antibiotic use in the United States is in livestock —cows, pigs, chickens, sheep, even farmed fish — either for medical reasons, like treating or preventing disease, or to promote growth. Most of the antibiotics used for humans are also used for livestock, said Dr. Karin Hoelzer, a veterinarian and microbiologist at the Pew Charitable Trusts, who has extensively studied antibiotic resistance.

Antibiotics are believed by many in the food production industry to promote overall health, increasing the number of animals that can be sold for food and improving the quality of the meat.

How can the use of antibiotics in animals pose a risk to humans?

There are several ways. The genes that produce resistance to antibiotics can be easily transferred between bacterial species. So resistant bacteria can pass their resistance to other strains.

Humans can come in contact with resistant bacteria through eating insufficiently cooked meat or other food products: Manure from animals fed antibiotics is commonly used as fertilizer for crops. Farmworkers and people who work in slaughterhouses may also come in contact with the bacteria, providing an opportunity for genes to be exchanged.

Have bacteria resistant to the antibiotic colistin been found elsewhere?

Colistin-resistant bacteria have been found in humans or livestock in countries on every continent, including China, Malaysia, South Africa, Egypt, Italy and several South American nations. Scientists have also reported finding colistin resistance in CRE in some countries, said James Spencer, a senior lecturer in microbiology at Bristol University in England who was a co-author on a 2015 study that reported for the first time finding the colistin-resistance gene in a form that could be easily transferred to other bacteria. The study looked at the presence of the gene in food animals in China.

Has the Food and Drug Administration regulated the use of antibiotics in agriculture?

Under F.D.A policies that will take effect Jan. 1, antibiotics that are considered “medically important” for humans will no longer be approved for use to promote growth in livestock.

The policies also require that a veterinarian supervise the use of antibiotics in feed or water for livestock. Currently, many of the drugs are sold over the counter and do not require the involvement of a veterinarian.

Compliance is voluntary. But the 25 drug companies that manufacture about 283 antibiotics approved for use in livestock have all agreed to change their drug labels to reflect the requirements.

Some critics, however, say they are concerned that the new policies will leave loopholes that could allow food producers to circumvent them.